A hybrid vehicle powertrain includes an electric machine such as an electric motor, wherein torque produced by an engine is supplemented with torque produced by the motor. The combined engine and motor torques are transferred to vehicle drive wheels through a transmission.
In a modular hybrid transmission (“MHT”) configuration, the engine is connectable to and dis-connectable from the motor by a disconnect clutch with the motor configured to directly drive the input shaft of the transmission. The engine, the disconnect clutch, the motor, and the transmission are connected sequentially in series when the engine is connected to the motor by the disconnect clutch.
During a process referred to as regenerative braking in a hybrid powertrain, charging a high-voltage battery during vehicle braking collects the potential and kinetic energy stored in the braking vehicle. During regenerative braking, required wheel braking torque is allocated between friction brakes and the motor, which acts as a generator. The amount of wheel braking torque required as the vehicle brakes is apportioned in real time by a controller between the hydraulic, mechanical friction braking hardware and the electric powertrain regenerative braking. The apportionment of wheel braking torque between friction braking torque and regenerative braking torque (i.e., negative input torque via the motor) is balanced through the braking process to achieve as much regeneration as possible to thereby improve fuel economy.